Astronomer Carolyn Porco describes that colorful swirly northern stripe here:
Over the past year, a great disquiet has swept across the face of Saturn. The normally serene countenance of this giant planet was pierced last December by the sudden eruption of a bright, discrete, and powerful convecting storm that over the course of two months grew and spread to become a planet-encircling colossus, a wide kaleidoscopic band of commingled waves, vortices, and eddies, all in continuous swirling motion …. a mesmerizing display of snaking, sensuous, churning, turning, chaotic, roiling atmospheric turmoil.
Saturn is now enjoying the equivalent of Earth’s mid-April. Orbiting the sun once every twenty-nine-and-a-half years, a month on Earth translates to the passing of about 25 hours on the ringed planet. A three-month season on Earth stretches out to a bit more than seven years on Saturn. Imagine a Spring that lasts so long, but only comes two or three times in one’s life. Imagine a Spring storm that takes two months to build and grow and sustains itself for a whole year.
Two other differences grace the ringed planet: those clouds are a few hundred degrees colder than the puffy whites of Earth. Totally different gases too. Saturn’s air is mostly colorless hydrogen and helium. The hues above are partly due to a camera sensitive to the wavelengths just beyond red–the infrared. What causes the coloration–the natural pastels of yellow, pink, and blue? Nobody knows.
Other features we do know about:
The thin blue line is the view of Saturn’s rings nearly edge-on from the Cassini spacecraft in this image.
Notice the ring shadows on Saturn’s cloud tops.
What’s that black dot in the lower left?
If you want to check Saturn’s progress from Earth, you’ll have to rise early in the morning. When I took the dog out about 6:30 AM today, Saturn was very high in the south, paired with the bright star Spica in the constellation of Virgo.